Engine cutting - Need a new ECU??

25th August 2009, 11:45

I posted on here a few weeks ago that when hot my Saxo VTS had started losing power - initially losing then regaining, then losing and not liking high revs, now just to the point where it decides enough is enough, the revs die of slowly until it cuts out.

It will run fine for a hour or so, then for example after coming of the motorway you put the hammer down and as soon as the revs go over 4500(ish) it starts cutting out. Once it starts it's only a matter of time until it cuts out and refuses to restart until it's had five minutes to cool down.

Various theories have been put forward for this -

- need new TDC sensor. Tried, Failed.
- need new Fuel Relay Switch. Garage has apparently tried this and it failed.
- fuel pump. Garage doubts this as the pump appears to be working and would not work from cold if it was that.
- Flywheel. Starting up makes a racket now, and initially the mechanic suspected the flywheel - but his theory has now moved on.

The new idea is that the ECU is dodgy and starts playing up at heat. It also has some idleing issues (revs dieing off), but again only when the engines warm. So he's planning on changing the ECU.

Does any one have any comment on whether this is likley to solve it, or if they have had similar?!

25th August 2009, 12:19

My cutting out issue was caused by faulty fuel pump.

Car would start okay (most of the time) and run alright, but under heavy acceleration it would cut out.

Also MAP sensor often causes cutting out.

Check for gasket leaks at manifold.

25th August 2009, 13:42

Quote:

Originally Posted by wall-e

My cutting out issue was caused by faulty fuel pump.

Car would start okay (most of the time) and run alright, but under heavy acceleration it would cut out.

Also MAP sensor often causes cutting out.

Check for gasket leaks at manifold.

This kind of starts at heavy acceleration, but then once it starts doing it it's only a matter of time before it goes, high or low revs.

I never have a problem with it starting at all (except just after it cuts out!), and I can be driving for an hour or more before I get any issues with it. I use the car for sprinting, and it would do it a bit on runs when at high revs in third, but never on the road, but over the past few weeks it's been getting progressivly worse - on the road.

25th August 2009, 14:02

Sounds like a pain.

Maybe you could get a diagnostic run, see if any faults are stored on the ecu?

Apparently lots of people have issues with weak fuel pumps, bit temperamental.. very easy to change yourself (not expensive for one from a breakers either)

The guys on here helped me get mine sorted.. they were 100% correct with their diagnosis.

25th August 2009, 14:08

Yeh tbh id start with a diognostics if your a bit puzzled with any of the quick fixes that havnt worked. See what comes up on the error log.

Try cleaning the sensors or swapping with someone elses VTS sensors and see if the problem persists.

Obviously something when its hot as youve said, and also when theres more of a surge of fuel etc as you said it happens when you hammer it. Possibly somthing to do with fueling.

Could be alot of things tbh lol. Start with a diognostics if you havnt already though.

25th August 2009, 16:17

My PnP ECU will fit your car, you're more than welcome to pop down and I'll stick it on for free if you like...

Kind of 'try before you buy'?

Andy

25th August 2009, 23:02

Thanks for the offered help - much apprechiated.

The garage have had it on a diagnostics machine twice - once from cold and once while it was playing up. Both didn't flag anything. Was talking to my Dad about his Mondeo and he said that never shows anything on diagnostics either.

Cheers for the offer luthor - the problem is it's so tempramental I'll probably end up driving round for well over an hour with the new one before I know if it's cured it or not!

1st September 2009, 17:46

OK - it's not the ECU. Had a recon ECU and a new Fuel Relay Switch fitted.

Drove it round with some gusto for half an hour with no problems, then in third, again at 4500 revs, it went again.

It's not a jolt, or noisy - it feels like I've just taken my foot off the accelerator - the revs just drop slowly, slowly, slowly until they are low enough for it to cut out. No amount of trying the throttle or changing up/down gears has any reaction what so ever - once the revs start to drop down they will go. Then I'm sat by the road for five minutes until it chooses to start again.

The garage's next idea is to change the temperature sensor as they think it's maybe not reading right. They don't sound very confident though!

1st September 2009, 17:54

take it you've change ht leads
given it a full service new sparkys etc
check idle control valve, 02 sensor, cleaned up throttle body just to make sure?

maybe try another garage with a differnt diagnostics machine....

1st September 2009, 17:58

Sounds like you need to find another garage. They sound clueless. Having diagnostic equipment is great, but in my experience few places know how fault find using the info they get from the gear, they just seem to aimlessly change parts.

1st September 2009, 18:19

Quote:

Originally Posted by baker556

take it you've change ht leads
given it a full service new sparkys etc
check idle control valve, 02 sensor, cleaned up throttle body just to make sure?

I mentioned the idle control valve to them and they said it wouldn't be that.

I'll give it some new spark plugs, but it's recently had an oil change anyway. Plus I'm not paying £100 for service - still just blindly chucking money at it then.

1st September 2009, 19:40

weak fuel pump id say or faullty coil pack

i have a load of sensors for sale if you need any